1. Field of the Invention
The present invention relates to an air intake system for an internal combustion engine of motor vehicles in general, and more particularly to an air intake device having a dual tube resonant chamber tuned to generate multiple frequency sound waves enhancing volumetric efficiency of the internal combustion engine.
2. Description of the Prior Art
In known air intake systems for internal combustion engines, the length and cross-section of the individual intake pipes are configured (or tuned) in such a way that the respective cylinders are filled to an optimum degree at a particular engine speed by a resonance effect. Such an arrangement is known in the art as a passive system meaning that it has a fixed geometry requiring no moving parts, as opposed to an active system. Tuning maximizes air flow by using sound energy (pressure) to help charge the cylinders. A sound wave travels toward an “open” end of an inlet duct due to an interaction of a piston motion and overlap function of valves. When this wave exits the “open” end of the inlet duct, a secondary wave (second order resonant wave) travels back toward an inlet manifold. A frequency (timing) of this wave is tuned by a length of the inlet duct. An optimal frequency is one that coincides within a few degrees of an inlet valve-closing event for an RPM point where a power is required.
Known induction tuning of intake manifolds of internal combustion engines has been carried out by various devices.
One of the conventional solutions resides in the so-called suction pipe charging wherein an intake opening of each engine cylinder is coupled with a suction pipe/resonance tube of predetermined cross section and length. On most road cars the length and diameter of an inlet runner are tuned for the lower end of the useable RPM band of the engine since this is where most daily driving occurs. The use of a single length and diameter effects an optimal tuning at a somewhat narrow power band. The reason is because the frequency dictated by the pipe length and diameter remains the same, while the valve-closing event occurs at different frequencies dictated by the engine speed. This phenomenon causes the frequency of the sound wave to have stronger and weaker effects on a cylinder charging as the engine speed changes.
An expansion chamber resonator is another such device, in which the induction airflow passes into a relatively large volume chamber, and thence into the engine. The expansion chamber prevents the formation of large amplitude standing waves and dissipates the sound energy in the system. However, the use of such resonator chamber devices often still result in a characteristic decline in engine torque at a particular narrow range of engine speeds, since expansion chamber resonators typically are not effective at all noise frequencies.
Yet another device is the “Helmholtz” resonator which comprises a chamber which does not receive the induction air flow, but is in communication with the air flow path via a small diameter opening. The resonance of the Helmholtz resonator is limited to a narrow range of engine speeds and thus is not effective over the entire operational range of engine speeds, and hence it has also been proposed to provide an adaptive Helmholtz resonator which is tuned differently over a range of varying engine speeds design.
Such approach, while effective, adds considerable complexity to the device.
Although those are effective strategies, they come at a cost as such gives up power at the top end of the engine speed range. In an effort to satisfy both of these competing interests, the automotive manufacturers have attempted to address this issue by making active, dual-path inlet systems, or moveable systems to broaden the power curve (known in the art as an active tuning). Unfortunately, developing an inlet design in this fashion is rather large, cumbersome, complex and expensive in manufacturing.
Thus, the need exists for a relatively simple, compact and inexpensive air intake device for internal combustion engines that increases the engine power and torque throughout a broad range of the engine speed in a passive manner.